1. Field of the Invention
This invention relates to a novel flame retardant additive for use in polymeric compositions. More particularly, this invention relates to an additive having amine salt and imide functions. Specifically, this invention relates to novel compounds consisting of bisimides containing halogen atoms and ammonium acid tetrahalophthalate.
2. Description of the Prior Art
A variety of compounds exist which impart satisfactory flame resistance, smoke suppression and self-extinguishing properties to polymeric compositions. U.S. Pat. No. 4,092,345 teaches the use of alkylene diammonium bis-tetrahalophthalates as flame retardants. A variety of other U.S. patents claim fire retardant compounds based on bisimides, dicarboxylic acids or dicarboximides.
U.S. Pat. No. 3,455,950 describes the use and preparation of N,N'-bisimides of polyhalosubstituted polyhydropolycyclicdicarboxylic acids. U.S. Pat. No. 3,748,340 relates to the bisimides of the above-mentioned acids. U.S. Pat. No. 3,574,230 describes haloaryl imides of polyhalopolyhydropolycyclicdicarboxylic acids.
U.S. Pat. No. 3,873,567 claims N-substituted polybromoaromatic ortho-dicarboximides. Canadian Pat. No. 961,589 relates to compositions comprising macromolecular inflammable materials, such as polymers, and a flame retarding amount of a broad range of bisimides.
It has now been discovered that bisimides containing halogen atoms and ammonium acid tetrahalophthalate groups are useful as flame retardants in polymeric compositions. These new compounds have increased thermal stability over prior art compounds, such as alkylene diammonium bis-tetrahalophthalates. The new compounds contain both ammonium salt and imide functions and foam on decomposition with the evolution of gas. This foaming effect is favorable in the preparation of flame retardant coatings.